Stretchable MXene-based humidity sensor arrays with high sensitivity and rapid response for proximity-sensing electronic skin

Stretchable electronic skins for touchless human-machine interfaces require accurate humidity sensing that is fully decoupled from mechanical strain interference. However, pristine 2D Ti₃C₂T_x MXene films suffer from restacking-induced sluggish kinetics and strain-induced resistance crosstalk. Herein, we report highly sensitive, rapid-response, and electromechanically isolated MXene-based humidity sensor arrays for proximity-sensing electronic skins. To enhance water molecule transport, MXene nanosheets are modified via alkaline intercalation to expand the interlayer spacing, followed by in situ polymerization of polydopamine (PDA) nanoparticles. The hydrophilic PDA aggregates act as hygroscopic spacers, modulating electron tunneling via moisture-induced swelling to achieve a high relative sensitivity of 0.707 /%RH and rapid response/recovery times (1.2 s / 2.3 s). To eliminate mechanical interference, the active composite is integrated onto a heterogeneous substrate consisting of glass-microfiber-reinforced stiff islands embedded in a compliant elastomer matrix. This architecture isolates the active film from strain-induced variations up to 300% strain. Utilizing liquid metal interconnects and a gas-permeable electrospun encapsulation, the fabricated 4×4 sensor array demonstrates high-fidelity spatial moisture mapping and non-contact gesture recognition even under 50% biaxial strain, offering a robust platform for advanced interactive robotics and personalized healthcare.